SECONDARY CONTAINMENT
Secondary containment to prevent pollution is an issue which crops up more and more in environmental regulations. Legally, tank farm owners are not only responsible for the cost of incidents, but also for the lack of action to prevent possible pollution - a fact that is causing operators to sit up and take notice. New tank farms are designed in such a way that any leaks from tanks are contained both horizontally and vertically. To contain leaks and spillage in the horizontal direction, tank pits are constructed with bund walls consisting of sand, clay, concrete, sheet piles and/or secondary tank walls. To stop the flow of potential pollution in the vertical direction, gasses and product are contained by means of secondary seals, domes and vapor recovery systems. Beneath the tank, the potential solutions include the installation of a second bottom (double bottom) or membranes. There are various reasons why a tank farm operator might choose one or the other solution. Few older tanks have liners or other secondary containment devices beneath them. Many tanks were built 20 or more years ago, when environmental regulations were less strict. But globally the awareness of the hazard of leaking tank bottoms is growing - and with this globalization, stricter rules are being applied worldwide. A second tank bottom is the requirement in some jurisdictions, and it is a rather cheap solution at the construction stage. However, the cost of maintenance and repairs could cause problems on the long run, especially where soil conditions are weak, humid and subject to continuous movements.
